1. Field of the Invention
This invention relates to a gas discharge panel, and to an improvement in an AC plasma display panel having a plurality of parallel electrode sets arranged transversely to each other on each of a pair of opposing substrates, which are coated with a dielectric layer to provide insulation of the electrodes from the gas filled discharge space.
2. Description of the Prior Art
Typically, in an AC plasma display panel, a plurality of electrodes are arranged on two substrates face to face across a discharge space, which is filled with gas such as neon (Ne) and display is achieved by causing selective discharge between chosen electrodes. In a gas discharge panel of this type, the structure and material of a dielectric layer on the electrodes greatly influences the operating voltages and service life. Therefore, various methods for improving dielectric layers have been proposed.
As described in the U.S. Pat. No. 3,716,742 to Nakayama et al, an overcoat layer composed of a heat resistant oxide is disclosed as being on the dielectric layer which insulates the electrodes. The overcoat disclosed in the Nakayama et al. patent may be directly or indirectly formed on the dielectric layer, which generally consists of low melting point glass containing PbO. The overcoat is seen as a protection layer for preventing sputtering damage from ion bombardment or as a secondary electron emissivity layer for lowering the operating voltage.
Materials that have been proposed for the overcoat layers are various metal oxides, oxides of rare earth elements such as CeO.sub.2 and La.sub.2 O.sub.3, or oxides of group IIA elements, known also as the alkaline earth metals.
U.S. Pat. No. 3,863,089, to Ernsthausen, shows that MgO (magnesium oxide) is in many ways a satisfactory material, since it has an excellent ion bombardment resistivity at the comparatively low operating voltages resulting from its comparatively high secondary electron emissivity. However, a panel with an MgO overcoat on the dielectric layer still requires sustaining voltages of 90 to 120 V and writing voltages of 100 V or more. However, these operating voltages are generally too high to be driven by integrated circuits. It is therefore desirable to reduce the operating voltages as low as possible in order to allow use of driving components which generate lower voltages and are lower in cost. It is also desirable to achieve a more stable operation by increasing the operating life of the panel.